Typewriting machine



June 5, 1945. R. VON REPPERT TYPEWRITING MACHINE Filed Jan. 11, 1944Patented June 5, 1945 TYPEWRITING MACHINE Richard Von Reppert,Rochester, N. Y., asslgnor to International Business MachinesCorporation, New York, N. Y., a corporation of New York ApplicationJanuary 11, 1944, Serial No. 517,780

2 Claims. (Cl. 200-122) This invention relates to typewriting machines,more specifically to typewriting machines which are operated by means ofan electric motor.

The primary object of the present invention is to provide means forimproving the operation of an electric motor used for operating atypewriting or other oflice machine.

An object is to provide means for improving the operation of electricmotors employing direct current.

An object is to improve the operation of the speed controlled type ofelectric motor wherein suitable centrifugal force actuated contact areused to regulate the speed of the motor.

An object is to provide an automatic reversing switch for. reversing thecurrent to an electric motor at periodic intervals.

An object is to provide an automatic reversing switch which iscontrolled by a thermal element.

An object is to provide a thermally responsive switching device withmeans for adjusting the time rate of operation of the thermal controlmeans.

Typewriting and other oilice machines operated by electric motors veryoften must be operated on direct current which may be the only availablecurrent for operating the motor. The motors used in office machines areusually of the constant speed, adjustable speed type, particularly intypewriting machines where the force of the blow of the type bars isregulated by controlling the speed of the motor. The speed of suchdriving motors is most commonly controlled by means of an adjustablerheostat of some form and the speed, once adjusted, is kept constant bymeans of a centrifugal actuated governor mechanism wherein the openingand closing of a pair of contacts, by controlling a resistance,maintains the speed constant at its adjusted value.

In the use of machines on direct current circuits, it has been foundthat a transfer of metal occurs from one governor contact to the otherowing to the polarity of the current which transfer continues until oneof the contacts has become so badly wasted away that the contacts eitherfunction haphazardly or fail to function. This wasting away of thecontacts is a well known characteristic of switching devices used indirect current circuits and arises from the are formed when the contactsopen. It has been found that when the direct current is periodicallyreversed the speed regulating contacts have a much longer life andoperate more satisfactorilyv An object of the present invention,therefore. is to provide a switching mechanism which will cause anautomatic reversal of the current at regular time intervals to preventthe wasting away of one contact and the building up of the other.

Other objects'cf the invention will be pointed out in the followingdescription and claims and illustrated in the accompanying drawing,which disclose, by way of example, the principle of the invention andthe best mode, which had been contemplated, of applying that principle.

In the drawing:

Fig. 1 is a longitudinal section;

Fig. 2 is a vertical transverse section on the line 2-2- in Fig. 1;

Fig. 3 is a vertical transverse section on the line 3-3 in Fig. 1 andshows the contact operating mechanism at the start of a cooling cycle ofthe thermal control element;

Fig. 4 is a view similar to Fig. 3 showing the contact operatingmechanism at the beginning of a heating period;

Fig. 5 is a wiring diagram.

The switch mechanism is housed in a one-piece cylindrical casing l0permanently closed at its right hand end (Fig. 1) and whichconventionally may be molded from a suitable plastic such as a phenoliccondensation material. This housing is covered at its open end by a capH which is provided with a suitable opening Ila through which passes theconnecting cables l2. Secured near the middle of the casing I0 is aflanged disk l3, preferably of metal, to which is secured a bearingbushing l3a acting as a journal for the shaft 14. This shaft is reducedat its ends, the right hand end being Journalled in the aforesaidbushing l3a, while the left hand end is journalled in a bushing carriedby an insulating disk H which is seated in the internal annular shoulderIlla formed in the casing [0. Disk I5 is held in place and kept fromrotating on the shoulder Illa by means of screws like I6 which passthrough holes in the casing l0 into radial holes in disk 15. The flangeddisk I! i also secured in any suitable manner to the housing It! toprevent its rotation within said housing.

In the space between the right hand end (Fig. ll of the housing I0 and.the'disk l3, adjacent said disk, is mounted thermostatic coil spring11. the inner end of which is connected to the shaft 14 (Fig. 2i whilethe other end is secured to the housing Hi. When this spring i heated ittends to increase in length thereby tending to rotate the shaft l4counterclockwise in Fig. 2, and when cooled tends to shrink and rotatethe shaft clockwise. Secured t0 the shaft I4 is a cam l8 (Figs.

3 and 4) formed with the cam surfaces I la, lib and the stop portionslBc which restrict angular movement of the shaft H and the cam H to anangle of approximately 60 by engagement with a stud I! carried by thedisk I3. Pivoted on the stud I! are the detents 20, 2| which areprovided with pins 20a, 2la held on the cam surfaces I80, I32; by meansof a common spring 22 coiled around the stud IS. The detents 20 and 2|are formed with teeth 20b and Nb, respectively, one of which normallyengages a locking notch 23a. or 23b in a locking disk 23 loosely mountedon the shaft H.

In Fig. 3, the right hand detent 20a. and its tooth 20b is engaged inthe right hand notch 23!) to prevent rotation of the locking disk 23 ina clockwise direction. In Fig. 4 the conditions are reversed and theleft hand detent 2| through its tooth 21b and notch 23a is holding disk23 against counterclockwise rotation. One or the other of the detents 2!is always operative to hold the looking disk against rotation.

The locking disk 23 is secured to a contact operating disk 24 (Figs. 1,3 and 4) through suitable posts 230 which space disks 23, 24 apart. Thedisk 24 is formed with two contact operating lugs 24a located ondiametrically opposite sides of the shaft H. Secured to the right handface of the disk l (Fig. l), which preferably is composed of insulatingmaterial, are four brackets 25 which support four sets of contactmembers 26, 21 provided with contacts 28a, 21a. The contact members 28,2'! extend approximately parallel with the shaft l4 and one of each pairis positioned to be engaged by the contact operating lugs 24a. In Fig.3, the lugs 24a are in a position to hold closed the contacts 21awhereas, in the alternate position of the disks 23, 24 of Fig. 4, thecontacts 28a are held closed. The brackets 25 not only act as supportsfor the contact members 26, 21 but also act as connecting straps wherebyeach contact 26a is electrically connected to one of the r. )ntacts 21a.

The cam I8 is provided with a pin l3d (Figs. 1, 3 and 4) the sides ofwhich are engaged by the parallel branches of a hairpin spring 28 partlycoiled around the shaft l4 and crossed between the pin lid and the shaftH as best shown in Figs. 3 and 4. The disk 23 is also provided with apin 23d which extends into the space between the two branches of thespring 23 and between the pin [8d and the shaft ll.

The operation of the mechanism so far described will now be explained indetail. Let it be assumed that the starting position of the parts isshown in Fig. 3 and that with reduction in temperature the spring ll isshrinking, tending to turn the shaft 14 in a clockwise direction in Fig.3 thereby rotating the cam I3 slowly at a speed which depends upon therate of change of temperature. The cam in will gradually urge the pin20a radially of the shaft ll until ultimately the tooth 20b will clearthe notch 23b and release the locking disk 23. As the cam 18 rotates ina clockwise direction, the pin |8d will rotate the right hand branch ofspring 28 thereby increasing the tension of the spring 23. However, thedisk 23 cannot follow the cam l8 for the time being because of the factthat the detent 20a prevents such action. When the tooth 20b finallyclears the notch 2317, however, increased tension of spring 28 willcause the disk 23 and the contact operating disk 24 to snap in aclockwise direction to the position of Fig. 4 in which the detent 2|,through lug H17 and notch 23a, locks the disk 23 againstcounterclockwise rotation. This, of course, causes the contacts 230 toclose and the contacts 21a to open as in Figs. 3 and 5. If now thethermostatic spring I1 is heated, it tends to rotate the cam I8 in acounterclockwise direction with the result that the pin 2|a. next isgradually moved radially by the cam lab until ultimately the tooth 2 lbclears the notch 23a. The counterclockwise rotation of the cam i8 causesthe pin IM to rock the left hand branch of the spring 23counterclockwise and increase the tension of the spring 23 in theopposite sense. Ultimately, the tooth 2lb will clear the notch 23a and,in consequence of the tension of spring 23, the disk 23 will be rockedin a counterclockwise direction back to the position of Fig. 3 toreclose the contacts 28a and open the contacts 21a.

For the purpose of controlling this action. which is produced byalternate heating and cooling of the thermostatic spring II, there isprovided an adjustable heater consisting of a suitable resistance coil23 (Fig. I) mounted in two concentric grooves 30a in a disk 30 ofinsulatin material, such as porcelain, which is mounted on an internalshoulder formed in the closed end of the housing ill but separated fromthe closed end by a circular rib I011. The heater unit is construct dsimilarly to a conventional rheostat or potentiometer and is providedwith a contact arm 3| secured to the left hand end of a slotted headstud 32. By turning the screw, the contact element 3| may be rotated toincrease or decrease the res stance of that part of the coil 28 which isincluded in the circuit (Fig. 5). By increasing the effective length ofthe coil the resistance is increased and the heating effect is reducedsince less current can flow through the increased length of coil. Also,increasing the length of the coil increases the heating time of the coilsince the heating effect varies inversely as the square of theresistance. In other words, the speed of heating will be increased byshortening the coil and decreased by lengthening the coil.

In Fig. 5, there is shown a wiring diagram illus trating the connectionof the heater coil or resistance 29 to the contacts 280, 21a. and themotor M.

When the parts are in the position of Fig. 4 with the contacts 23aclosed and contacts 21a open, the heater 2! is operative and current isflowing in a given d'rection through the motor M. When the thermostaticspring I! has rotated the cam disk H! from the position of Fig. 4 to theposition of Fig. 3 to efi'ect the closure of contacts 21a, the heater 23is shunted by one pair of the contacts 21a thereby a lowing the heaterand the thermostatic spring I! to cool and gradually move the parts backto the position of Fig. 4. At the same time. the closure of the otherpair of contacts 21a effects a reversal in a direction or the currentthrough the motor M which, of course, does not effect its direction ofrotation but does change the polarity of the speed control contacts 33(Fi 5).

For the purpose of romoting rapid cooling of the spring H, the housingI0 is provided with ventilating holes llc which also prevent overheatingof the switch in the event cam I! should stick in the position in whichthe heater element 23 is operative. In order to prevent the switchmechanism from becoming overheated there is provided a washer 34 of heatinsulating material such as asbestos. This also assists in producing afast snappy action of the switch since a large amount of heat stored inthe metallic parts would tend to retard the rate of cooling of thethermostatic element 11.

While there have been shown and described and pointed out thefundamental novel features of the invention as applied to a singlemodification it will be understood that various omissions andsubstitutions and changes in the form and details of the deviceillustrated and in its operation may be made by those skilled in theart, without departing from the spirit of the invention. It is theintention, therefore, to be limited only as indicated by the scope ofthe following claims.

What is claimed is:

1. In a thermally responsive switch, contact means, an oscillatablemember for operating said contacts and in one position holding thecontact means open and in another alternate position holding saidcontact means closed; a pair of latches coacting with said member tohold it in the open contact and closed contact positions, respectively,one latch for each position, one of said latches normally holding saidmember against movement to the alternate position to thereby hold saidcontact means open, a release member oscillatable between alternatepositions to release said latches, a thermal element operative whenheated to actuate the releasing element to release I the latch normallyholding the first member and thereby enable the first member to move toa position to close the contact mean'sfa heater in parallel with saidcontact means and operative to heat said thermal element when thecontact means is open to thereby cause the release membar to move to thealternate position and release to its other position when a latchholding it in one of its ositions is released, and a second contactmeans actuated to open and closed position by said first member, andmeans to vary the heating effect of said heater.

2. In a thermally responsive switch, contact means, an oscillatablemember for operating said contacts and in one position holding open thecontact means and in another alternate position holding said contactmeans closed; a pair of latches coacting with said member to hold it inopen contact and closed contact positions, respectively, one latch foreach position, one of said latches normally holding said member againstmovement to the alternate position to thereby hold said contact meansopen; a release member oscillatable between alternate positions torelease said latches, a thermal element operative when heated-to actuatethe releasing element to release the latch normally holding the firstmember and thereby enable said first member to move to a position toclose the contact means, a heater in the form of an electricalresistance in parallel with said Contact means and operative to heatsaid thermal element when the contact means is open to thereby cause therelease member to move to the alternate position andrelease the latchholding the first member in open contact position, spring means betweensaid members tensioned when said releasing member is moved from onelatch releasing position to the other and operative to actuate the saidmember to its otherposition when a latch holding it in one of itspositions is released, a second contact means actuated to open andclosed positions bysaid first member, and means to variably cut in orout part of said resistance to vary the heating eflect of said heater.

, RICHARD VON REPPERT.

